Origin and Habitat: Eriosyce tenebrica is common from west of Domeyko to the valley of the Rio Choros in the Chilean regions of Atacama and Coquimbo (West of the territory of the Eriosyce napina var. fankhauseri)Habitat and ecology: It occurs in rocky soil with good drainage in coastal vegetation together with Oxalis gigantea and Eulychnia breviflora, mainly in large ravines and valleys that reach the coast of the Region of Atacama, between 300 to 750 meters. It grow flat with the ground and is often covered by dark brownish sand and dust.

Subspecies, varieties, forms and cultivars of plants belonging to the Eriosyce napina group

Eriosyce napina(Phil.) Katt.: Tiny geophyte, with a solitary sphericalstem slowly growing atop a thick, underground taproot, with a constriction between the stem and the root. Spines: short black, flattened against the stem surface. Distibution Huasco to 15 km south of Freirina.

Eriosyce napina subs. challensisI.Schaub & Keim: It appears white due to its very woolly areoles and addpressed spines that make it looks like a tiny hairy Epithelantha.

Cultivation and Propagation: This species has the fame to be difficult to grow, but it is really not so difficult. Whatever view one adopts, it is worth a place in every cactus collection. The only problem is that it is very slow growing and for its long root, necessitates a rather larger, or deeper at least, pot that one might expect for the size of plant. Like all thick-rooted species, it requires careful watering (rot sensitive), and patience to match its slow growth. During the winter rest, the plant may pull near the surface of the potting mix. Sometimes they are grafted to avoid root rot problems. Suited for sunny-bright exposure; they can tolerate light shade. They prefer airy exposures. They like warmth (recommended minimum winter temperature 5° C). But plant kept perfectly dry can easily survive in winter night temperatures below 0° CPests & diseases: It is especially prone to rot, therefore, underpot in a smaller container filled with a very porous compost.Propagation: Direct sow after last frost (it usually doesn't produces offsets) or graft. Seeds can be sown in the spring or summer. The seedlings should not be disturbed until they are well rooted, after which they can be planted separately in small pots.